new to me too! any chance of a source on this mr WoW.com?

Perhaps I'm missing something in the article, but I don't believe that's true. As far as I understand it, the RNG for quest drops in completely random, not cumulative or additive in any way. At least that's always been my understanding, that there is one RNG for all game processes that depend on chance - including loot/object drops.

I think you have missed something:

"Getting skunked by the RNG? Once you reach Northrend and Wrath of the Lich King content, drop rates for quest items are progressive. The more monsters you kill, the higher your chance of receiving the widgets they drop."

is what we are refering to.

I can't remember the source but it was quite a while ago, and as far as I know if an item has a 10% drop rate, then on the tenth kill of it not dropped it is a 100% dropr ate I think.

It's likely that this scales per kill so:

Kill 1- 10% drop rate,
Kill 2 - 20% drop rate,
etc

Once the item drops it resets back to previous drop rate.

The bit about it increasing per kill is speculation, the thing about it becoming a100% after a number of kills I definitely read somewhere.

It's a Blue-stated fact that there is something in-game that makes it work that way. Didn't know whether or not if was just Wrath content or all of it. Hopefully it's worked into old Azeroth with Cata.

here is the source info
http://www.wow.com/2009/03/28/progressive-drop-rates/

@sprout_daddy
ONLY for WotLK quests and areas, they introduced a progressive drop-rate where the base drop rate has been increased to 45% from 35% and each kill increases the drop rate by a little(not specified) until it eventually reaches 100%. For classic and BC zones and quests, quest item drops at a static 35%.

Here's a wow.com link:
http://www.wow.com/2009/03/28/progressive-drop-rates/

Thank you for clarifying that - I should L2Read :-)